1. Field of the Invention
The present invention is directed to a vane wheel, in particular an impeller wheel or turbine wheel, for a hydrodynamic coupling device comprising a shell which is rotatable about an axis of rotation during operation, and a plurality of vanes which are arranged at the shell successively in the circumferential direction, each of the vanes having at least one connection projection which is inserted into a connection recess provided in the shell.
2. Description of the Related Art
A vane wheel for a hydrodynamic coupling device, in particular in the form of an impeller wheel, is known from U.S. Pat. No. 3,550,234. In this impeller wheel, a plurality of vanes arranged successively in the circumferential direction and extending approximately radially are fixedly connected with an outer shell, designated hereinafter simply as xe2x80x9cthe shellxe2x80x9d. To this end, depressions are provided in the shell at two different radial areas opening in the direction perpendicular to the area of the shell in which they are arranged. In a corresponding manner, each of the vanes has projections which are insertable into these depressions by lever-like movements. Before the vanes are inserted into the shell, they are plated with copper in an electroplating process. An inner shell is optionally arranged at the inner side of the vanes after the vanes are arranged on the outer shell. The assembly including the shell, the vanes and, as the case may be, an inner shell is then placed in an oven and the copper plating is melted. The small intermediate space between the vanes and the shell and/or the inner shell is then filled with the melted copper by capillary action, so that the vanes are connected with the shell along their entire radial length.
A problem with this know connection of the vanes to the shell is that after the shell, which is generally made of a sheet metal part, has been shaped and undergone a cold hardening to reinforce the shell, some of the effects of cold hardening are lost when heating the assembly composed of the shell and vanes to secure the vanes to the shell. This reduces the stiffness and stability in the entire wheel. The known process has a high energy requirement because (1) the vanes must be coated with copper or some other soldering agent in an electroplating process and (2) it is necessary to heat the entire wheel. Furthermore, the heating step also significantly lengthens the production period for the entire wheel.
It is the object of the present invention to provide a vane wheel, in particular an impeller wheel or turbine wheel, for a hydrodynamic coupling device which can be produced economically and with a high degree of stability. Further, a process for the production of a vane wheel of this kind is provided.
According to a first embodiment of the present invention, the object is met by a vane wheel, in particular for an impeller wheel or turbine wheel, for a hydrodynamic coupling device, comprising a shell which is rotatable about an axis of rotation in operation and a plurality of vanes arranged at the shell successively in the circumferential direction, wherein each vane has at least one connection projection which is inserted into a connection recess provided in the shell.
In the vane wheel according to the present invention, it is further provided that the each vane has a fastening projection. The vanes are fixedly connected with the shell in the area of the fastening projection.
Since the vanes are fixedly connected with the shell in the area of their respective fastening projections, the vane wheel according to the present invention does not require the vanes to be soldered with the shell along their entire radial extension, for example, by coating with a solder.
The connection of the vanes with the shell at the fastening projections may be carried out, for example, by riveting and/or welding, preferably laser welding. Each vane comprises a planar sheet arranged in a vane plane. It is possible that the fastening projection is rotated with respect to the vane plane for contact at a surface region of the shell.
At least one rivet insertion opening may be provided at the fastening projection, wherein a rivet provided at the shell may be inserted into this at least one rivet insertion opening. Furthermore, the rivet insertion opening may be constructed so as to widen in one insertion direction. Due to the widening in the rivet insertion direction, a secure axial hold may be achieved between the shell and the corresponding vane after the deformation of the rivet projection even when the rivet projection has no pronounced rivet head area after shaping but is only expanded essentially radially (with respect to its longitudinal axis).
When the connection projections of the vanes are inserted into the connection recesses in the shell, small intermediate spaces are formed which would allow a movement play of the vanes in the circumferential direction. These small intermediate spaces would result in rattling noises during operation. To prevent rattling during operation, each vane is connected with the shell in the area of its fastening projection such that at least one connection projection is arranged in the associated connection recess accompanied by tensioning.
To ensure a high degree of stability in holding the vanes at the shell when no solder connection is provided over the entire radially extending area between the vanes and shell, the vanes may include a first connection projection in a radial outer area and a second connection projection in an area lying farther inside radially. The shell has a first connection recess and a second connection recess located farther inward radially corresponding respectively to the first and second connecting projections.
Another problem in the vane wheel known from the prior art which complicates production is that the connection recesses are open in a direction substantially normal to the surface of the shell in which they are arranged. Since the shell is curved and not planar, the production of these recesses must be carried out in a very costly process because depressions extending in this manner cannot be introduced simultaneously during the deep drawing process. Furthermore, an elaborate tool must be employed to generate these connection recesses. To avoid this problem, each vane may be guided, or is guided, into the respective associated first and second connection recess in the direction of the axis of rotation by its first and second connection projection. The axial insertion simplifies the connection process appreciably because the lever-like movement requiring a swiveling movement of the individual vanes need no longer be carried out as it was in the prior art. Also, the entire shell may be shaped in a single deep drawing process from a metal blank because no undercuts or the like are formed in the axial direction.
In known hydrodynamic coupling devices, there is a general tendency for the vanes to detach from the shell axially. To counter this tendency, it is further advantageous in the design of a wheel according to the present invention to provide a safety arrangement for holding the vanes at the shell in the radial outer area to prevent the vanes from moving in the axial direction. This is especially advantageous when the respective fastening projections are positioned in the radial inner area of the respective vanes.
The safety arrangement may comprise a retaining ring positioned so as to adjoin the first connection recesses in the axial direction or the first connection projections arranged therein. This retaining ring may be held at the shell by pretensioning and/or welding or the like.
According to another embodiment, the present invention is directed to a process for producing a vane wheel, in particular an impeller wheel or turbine wheel, of a hydrodynamic coupling device comprising the following steps:
(a) providing a plurality of vanes, each vane having at least one connection projection and a fastening projection;
(b) providing a shell having a connection recess corresponding with each of the at least one connection projection;
(c) inserting the vanes in the shell by inserting the connection projections into the corresponding connection recesses; and
(d) fastening the vanes to the shell in the area of their fastening projections.
Step (a) of the process may comprise providing the vanes with a fastening projection which is rotated with respect to a vane plane. Alternatively, or in addition to the rotation of the fastening projection, step (a) may comprise providing the vanes with a radial outer first connection projection and a second connection projection located radially inward from the first connection projection and step (b) may comprise providing the shell with first connection recesses associated with the first connection projections and second connection recesses associated with the second connection projections.
It is further advantageous when step (b) comprises providing the shell with a fastening rivet projection for the fastening projection of each vane, wherein each of the fastening projections comprises an opening in which the fastening rivet projection may be fitted. After the fastening projection is fitted to the fastening rivet projection, the fastening projection of the vane can be fixed by deformation of the fastening rivet projection and/or when step (b) comprises providing the shell with a surface region at which the respective fastening projections of the vanes can be fastened by welding on, preferably by laser welding.
To simplify the production process as well as the assembly process as much as possible, it is suggested that step (b) comprises providing the shell with connection recesses such that in step (c) the vanes are inserted into the connection recesses with their connection projections by axial movement with respect to the shell. Step (b) may then also comprise providing the shell with connection recesses which are all open axially.
To improve the fixing of the individual vanes to the shell, the process according to step (c) further comprises a step (e) for positioning a safety arrangement at the shell for holding the vanes axially at the shell.
In this respect, step (e) may, for example, comprise arranging a retaining ring at the shell so as to axially adjoin the first connection recesses or the first connection projections arranged in the first connection recesses.
To prevent the occurrence of a slight circumferential movement play between the vanes and the shell, step (d) may comprise fastening the fastening projections to the shell in such a way that the connection projections are received in the associated connection recesses under tensioning.
Step (a) may further comprise, for example, stamping the vanes out of a metal blank and, where appropriate, shaping the stamped parts.
It may be further provided that step (b) comprises stamping the shell out of a metal blank and subsequently shaping the stamped out part to form the shell.
To simplify the production process, it is suggested that the shaping process is carried out at the same time as the forming of the connection recesses and/or the forming of fastening rivet projections at the shell.
The present invention is further directed to a hydrodynamic coupling device in which at least one of the turbine wheel and the impeller wheel comprises the vane wheel according to the present invention, wherein the vane wheel is preferably produced by a process according to the present invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.